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ozpiper

Two Questions that need answered.

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Hi all.......

I have a Realistic STA-82 Receiver that was working fine until the other day. FM radio works beautifully through both my Sony S30 speakers, but now when I swith to my turntable, one speaker sounds like a storm is happening. The other speaker is fine. (I can change the speakers over  and the same thing happens)

Now, as I don't know much about electronics: My first question is:

 

Is it worth paying out money to get this repaired?, or should I sell it "as is?"

 

And my second question is:

 

If it is worth getting repaired, is there anyone on the Gold Coast would could do it?

20200725_143255.jpg

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Posted (edited)

As the fault occurs on the turntable / phono selection, the first thing to check is your phono cartridge lead out wires located just after the cartridge, as one of those being loose can cause disconnection of the signal earth.  Next would be the RCA cables for the phono input similarly having disconnection of earth, and lastly that your turntable has installed a additional earth wire installed to a earthing post at the rear of your receiver, can assist excess noise, but much more likely a disconnection of the cartridge to phono input cabling earth or with slightly less noise its positive leads.

 

A multimeter can be used to check for continuity from cartridge to phono cables, with turntable off, and receiver OFF  arrange the multimeter to read OHMS and measure each cartridge lead out wire - you should get close to 0.02 ohms or so for each cable, measuring to the RCA ends.  There will be 4 cables to check, namely R + , L+ and L Gnd and R Gnd. If one is open circuit- there is your fault, which could save a trip out to be repaired. 

 

Less likely is a fault with the phono preamp in the receiver, in which case if the prior checks are OK, will need referencing to the schematic here, printing it will help the person repairing for you.

  https://www.hifiengine.com/manual_library/realistic/sta-82.shtml

Edited by stereo coffee

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Sounds like the volume and other controls need a good clean , they do go for around $175 to $225 even more in great cosmetic condition. Try whilst turned off sliding the volume control up and down rapidly to see if that makes a difference. It shouldn't cost too much to repair unless other faults are found like a cap going out even then it won't cost too much. There's a thread on repairers on stereonet and locations 

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Reads like you have a failing transistor (in one channel) in the phono stage. Since FM works fine and other phono channel is ok. Probably diy repairable, source parts from RS, probably $2- Will try and track down service manual.

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Phono stage has 2 transistors (2SA640, 2SC1000) and 3 electrolytic caps per channel. The 2SC1000 has some history(AK site) of going noisy. Less than 1 hours work to replace transistors and caps on both channels.

 

Oxidation on switch contacts is a common issue in vintage. While playing something on phono, gently rock the function selector switch back and forward a few time, then fully switch a few times and note any effect, might cost you nothing.

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What an unbelievable collection of knowledge is found here on this forum!!

😲

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Switch/swap the phono RCA connections into the amp over, ie, left phono plug into right socket, likewise right phono plug into left socket. Does the distortion stay on the same channel/spkrs? (indicates amp issue) or has it swapped channels (indicates cabling, cartridge,wiring... issue)

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MBZ....i swapped the rca plugs over and the sound comes out of the same speaker. In fact, with both the red and white rca jacks out.....it still had that sound in the speaker.

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Might still be a switch issue... as above, rock the function selector switch back and forth. Wouldn't hurt to exercise all switches but function selector prime candidate since problem only occurs on phono. Assume you've tried something connected to AUX.

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Have turned the selector switch multiple times and no difference.

I don't have any connectors to try my cd player in my aux port.

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17 hours ago, ozpiper said:

Have turned the selector switch multiple times and no difference.

I don't have any connectors to try my cd player in my aux port.

Looking like a phono stage issue, would be nice to run the CDP/AUX test before you start spending money.

Some of the caps in phono stage may be polar tantalum, these have some history of going noisy (windy/stormy, see AK site).  Candidates for replacement would be TR501a,b(2SA640, low probabilty, replace with KSA992), TR502a,b(2SC1000, high probability, replace with KSC1815), C501a,b(4.7uf/16V, low, however high if tantalum), C503a,b 10uf/16V(low), C506a,b 33uf/6.3V(low), C507a,b(1uf/50V, high if tantalum). The tech could/(should) use an oscilloscope to confirm the source of the noise.

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